Emissive displays produce images made up of many pixels. Such displays commonly control the color and brightness of each pixel to present an image. A pixel is in turn often composed of multiple sub-pixels of different colors. The human eye typically does not perceive a sub-pixel individually. Instead the eye blends the sub-pixels together producing the impression of a single uniform pixel. The color and brightness of a pixel may be controlled by varying the brightness of the underlying sub-pixels. For example, the underlying sub-pixels may produce a white pixel by illuminating with equal intensity. The underlying sub-pixels may produce different pixel colors by changing their relative brightness. The size of the single uniform pixel, which determines the resolution of a display, is typically equal to the sum of the sizes of its constituent sub-pixels and or the smallest feature that a display can resolve.
Display manufacturers may select sub-pixels colors to coincide with the cone cells of the human eye. Cone cells are primarily sensitive to red, blue, or green light. Accordingly, most displays implement sub-pixels of red, blue, and green emitters. These three colors may be combined to span a range of perceivable colors while minimizing the size of a pixel. However, such pixels are often unable to reproduce colors with a wavelength greater than that of the red sub-pixel or a wavelength less than that of the blue sub-pixel. A display may produce colors outside of these color ranges using additional sub-pixels, at the cost of increasing the individual pixel size and loss of resolution.